A prior art pressure washer is designated as 50 in FIG. 3. The pressure washer 50 includes a positive displacement pressure washer pump 160 having at least four ports, two of which are designated as 162 and 164, and two of which are opposite the ports 162 and 164 but not visible in FIG. 3.
An unloader valve 100 is placed in fluid communication with the pump 160 via two of the four ports. The unloader valve 100 has an inlet port 112, an outlet port 114, and a by-pass port 116. The outlet port 114 is placed in fluid communication with a spray gun or other release mechanism (not shown).
The inlet port 112 is placed in fluid communication with the pump port opposite the port 162. In particular, a first elbow fitting 67 is connected to the inlet port 112, a second elbow fitting 67 is connected to the pump port, and a nipple 68 is interconnected between the two elbow fittings 67.
The by-pass port 116 is placed in fluid communication with the pump port 164. In particular, a hose barb 187 is interconnected between the by-pass port 116 and one end of a by-pass hose 76; another hose barb 187 is interconnected between an opposite end of the by-pass hose 76 and an inlet fitting 180; and an opposite end of the inlet fitting 180 is threaded into the pump port 164. Each end of the by-pass hose 76 is secured to a respective hose barb 187 by means of a hose clamp 178. An inlet filter 188 is disposed within the inlet fitting 180.
When the pump 160 is running and the spray gun is in use (the trigger is pulled), water flows into the inlet port 112 on the unloader valve 100 and out the outlet port 114. When the pump 160 is running and the spray gun is not in use (the trigger is released), water flows into the inlet port 112 on the unloader valve 100 and out the by-pass port 116. An adjustment knob 118 allows a user to adjust the amount of pressure in the water that is available to the spray gun.
A pop-off valve 120 is placed in fluid communication with the pump 160 via the port 162. In particular, one end of the pop-off valve 120 is threaded into the port 162. If water pressure exceeds a maximum threshold level, the pop-off valve 120 discharges water from the system. In this respect, the pop-off valve 120 is designed to be the weak link in the system from the standpoint of pressure.
A thermal relief valve 130 is placed in fluid communication with the pump 160 via the port opposite the port 164. In particular, one end of the thermal relief valve 130 is threaded into the port. If water temperature exceeds a maximum threshold level, which is more likely to happen when the pump runs too long in the by-pass mode, the thermal relief valve 130 discharges water from the system. In this respect, the thermal relief valve 130 is designed to be the weak link in the system from the standpoint of temperature.
The prior art pressure washer 50 is satisfactory in many respects but still leaves room for improvement. For example, numerous pieces of hardware are necessary to interconnect the various ports and valves. Also, this prior art system 50 uses all four of the ports on the pump 160.